In response to the urgent need for sustainable alternatives to fossil products and the promotion of a circular economy, biorefineries offer an effective strategy for biomass valorization. Jatropha curcas L., a drought-tolerant species native to Mexico and Central America, is well known for its oil-rich kernels; however, its seed coat remains largely underutilized, limiting the full exploitation of the crop.

This study presents the first integrated biorefinery model for the comprehensive valorization of JCL seeds, converting both kernels and seed coats into high-value biofuels, materials, and nutritional and chemical co-products through sequential fractionation and conversion.

The kernel was subjected to mechanical oil extraction at 200 °C, followed by transesterification with 1% NaOH to produce biodiesel (ASTM-D6751). Residual protein cake from extraction was refined with isopropyl alcohol to obtain molasses. In parallel, milled seed coat underwent alkaline (NaOH 4.5%, 80 °C, 2 h, 4 cycles) and subsequent bleaching treatment (chloride-based, 80 °C, 4 h, 4 cycles) to disrupt lignin–carbohydrate complexes, yielding lignin- and cellulose-rich fractions. The cellulose-rich fraction was then processed into cellulose nanofibrils by high-pressure homogenization (10000 psi, 10 cycles).

This integrated approach achieved ~85% total biomass seed valorization. Kernels accounted for 69.0 ± 2.8% of seed mass, with oil extraction yielding 45.0 ± 2.5% and residual protein cake 47.3 ± 1.0%. Of this extracted oil, 90.3 ± 3.4% was converted into biodiesel, while 9.4 ± 2.8% remained as glycerol. Molasses were produced for first time from the protein cake, representing ~10% of its mass and leaving ~37% as purified protein. The seed coat represented 30.1 ± 3.1% of seed mass, yielding 21.5 ± 3.4% of lignin-rich fraction from the generated black liquor after alkali treatment, and 44.6 ± 2.4% of cellulose-rich fraction from bleaching. The cellulose-rich fraction was then processed into cellulose nanofibrils of 5 nm of diameter without previous pre-treatment.

These findings demonstrate the potential of JCL as a versatile feedstock for sustainable bio-based industries.

Acknowledgments: RM is grateful for Grant RYC2021-034380-I funded by MCIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU”/PRTR.